1. Field of the Invention
The present invention relates generally to hoists, and in particular to a construction materials hoist for mounting on scaffolding.
2. Description of the Prior Art
In the construction industry, materials, workers and equipment must often be elevated from lower levels on construction sites to higher levels where their presence is required. Various types of cranes, hoists and elevators have heretofore been utilized to accomplish these tasks.
Temporary scaffolding is commonly employed in construction to provide elevated staging areas for materials, workers and equipment. Such scaffolding is available in generally rectangular frames, which are set up in pairs interconnected by diagonal bracing to form relatively rigid scaffolding frameworks. The frames are often stackable so that scaffolding systems can be assembled to various heights. Typically, planks are extended between the spaced scaffolding frames to provide staging areas for the materials, workers and equipment.
An exemplary use of such a scaffolding system is in masonry construction, which often requires the elevation of relatively large amounts of materials. As the masonry construction progresses upwardly, mortar and the masonry units (e.g. bricks, blocks, stones, etc.) are lifted to staging areas on the scaffolding system at appropriate heights.
On many masonry construction jobs, the materials are elevated entirely by manual laborers known in the industry as "hod carriers". However, manually stocking an elevated work staging area with masonry materials tends to be relatively time-consuming and expensive, especially since hod carriers normally lift only ten bricks or so at a time. Naturally, the time and expense of manually stocking a staging area increases with the height to which the materials must be elevated. To reach a staging area atop multiple scaffolding levels, the materials must be lifted and set down through a series of intermediate staging areas, the vertical separation of which is limited by the height that a hod carrier can elevate the materials in one motion.
To overcome some of the aforementioned problems associated with manually elevating construction materials to scaffolding staging areas, hoists have heretofore been combined with scaffold systems. For example, the Isbell U.S. Pat. No. 2,985,428 shows a scaffold structure with a pair of winch mechanisms for raising and lowering a work platform. The Wardell U.S. Pat. No. 2,829,929 shows a scaffold assembly with a hoist carriage movably mounted on vertical trackway sections. A crane assembly is provided for raising and lowering the hoist carriage by means of a cable attached to the carriage and to suitable hoisting machinery. However, such prior art hoist and scaffold combinations tended to be relatively complex, incompatible with existing scaffolding systems, difficult to set up and take down, and otherwise generally unsuited for many construction projects requiring the elevation of materials, workers and equipment. Consequently, on many construction projects, materials, workers and equipment are still manually elevated in much the same manner as they have been for centuries.
The present invention addresses the aforementioned problems.